A. Field of the Invention
The present invention relates to an apparatus for treating ULSI (ultra large scale integration) semiconductors such as a Si wafer in specific atmospheric conditions, such as high-temperature and high-pressure conditions. It, more particularly, relates to an apparatus for treating semiconductor substrates typically in units of one lot made up of 13 or 25 sheets of substrates. Still more particularly, the invention relates to a high-temperature and high-pressure gas furnace for use in treatment of semiconductors to remove voids existing thereon chiefly by the use of inert gas pressure, and a method for treating a wafer on which a wiring film of aluminum alloy or copper alloy has been formed by a PVD method (physical vapor deposition), by applying pressure of an inert gas thereto, the so-called pressure fill process of wiring film (high-pressure reflow process).
B. Description of the Related Art
Fabricating processes of semiconductor wafers are known. Such processes include pressure treatment with the use of gas pressure, methods to treat a wafer under pressure in an inert gas, where the wafer includes a wiring film of aluminum alloy or copper alloy is formed through the PVD method, the so-called pressurized fill process of the wiring film (high-pressure reflow process).
Further, as a process for treating semiconductors is known which includes the use of high-pressure gas up to the level of several tens of atmospheric pressure, and a high-pressure oxidizing method causing the surface of the Si wafer to oxidize forming an insulating layer is known. In this case, because the objective of the process is oxidization, oxygen or water is naturally mixed in the pressurized medium.
In the known method, an apparatus is known performs high-pressure treatment of the semiconductor one by one as each wafer has gone through the PVD process, i.e., that of the so-called single wafer cluster tool type. As disclosed in the gazette of Japanese Patent Laid-open No. Hei 7-193063, for example, the apparatus is configured to process a wafer moved into a lock chamber by moving it through a series of processing modules disposed around a core chamber one after another by means of a transport arm within the core chamber. One of the modules is a pressure treating module directly mounted on the core chamber. An example of such a detailed structure of a pressure module is proposed in the gazette of Japanese Patent Publication No. Hei 7-502376.
An apparatus for use in the latter method is disclosed in the gazette of Japanese Patent Laid-open No. Hei 4-234119 is known. Although this apparatus is for a completely different use from the use of the present invention, it is mentioned here just for reference as an example of known apparatuses because both are of similar structure.
Namely, this apparatus is an apparatus for treating semiconductor wafer comprising: a pressure vessel; a hollow member with a treating chamber incorporated therein disposed within the pressure vessel, said hollow member having an opening at the lower portion thereof for receiving the wafers when said pressure vessel and said hollow member move a plurality of wafers as a unit each time of treatment from a position at the lower portion of said pressure vessel into said treating chamber; movement means capable of moving vertically with respect to said pressure vessel for shutting said opening; means coupled with said hollow member for introducing a pressurized oxidizing agent into said treating chamber; means for introducing a pressurized inert gas into said pressure vessel; means for heating the oxidizing agent within said treating chamber; means for cooling said hollow member after the wafers have gone through treatment within said treating chamber; and means coupled with said pressure vessel and said hollow member for equalizing pressures of the inert gas and the oxidizing agent and coupled with the body of the apparatus for equalizing the pressures of the inert gas and the oxidizing agent, thereby essentially separating said inert gas from said oxidizing agent.
As an apparatus for treatment under high-temperature and high-pressure conditions by using a pressurized gas, a hot isotropic pressure apparatus (HIP apparatus) is known and there is one, as an example, that is disclosed in the gazette of Japanese Patent Laid-open No. Sho 63-41787.
The apparatus of the single wafer type mentioned first above (the first prior art example) is different in the manner of treatment from the present invention. Therefore, it has a greater problem resulting from the treatment itself rather than that of a defect in the structure of the apparatus. Namely, in the first prior art example, each wafer is processed on a one-by-one basis and because of the cycle of time required, the process cannot be performed at the same rate a PVD process, which is performed in parallel. Therefore, the first processing of each wafer slows down the overall process. Therefore, components including the sealing structure and material at the opening and shutting portion of the vessel are subjected to very severe conditions and therefore it is quite difficult to secure the safety and reliability on the treatment.
The high pressure oxidization apparatus mentioned second above (the second prior art example) performs operation with inert gas introduced therein when no oxidizing agent is introduced. Here, since the apparatus of this kind is originally designed for an oxidization process, air unavoidably entering the high pressure vessel when articles to be treated are taken into and out of the vessel has not been considered, i.e., no consideration has been given to mixing in of oxygen accompanying the mixing in of air. Therefore, when it is intended to operate the apparatus as a high-temperature and high-pressure gas furnace that will process semiconductors, as the articles of fabrication in the present invention, in the conditions close to a completely inert environment, especially in the environment free from oxygen, it appears to provide unsatisfactory results.
Lately, copper has come more attractive than Al as the material of the wiring film in view of its low electric resistivity and its characteristics against EM (Electron Migration) and it is desirable to also apply the pressurized fill process to the wafer after the film has been formed thereon in the fabrication of ULSI which are getting more and more micro-miniaturized. In this case, when the wafer after the film has been formed thereon is handled in the atmospheric air, it is feared that the copper film is oxidized and the pressurized fill process is thereby disturbed. In any of the related arts mentioned above, no consideration has been given to countermeasures against such oxidization.
The invention is aimed at the provision of high-temperature and high-pressure gas furnace in which the above enumerated problems are solved. More concretely, it is an object of the invention to provide a high-temperature and high-pressure gas furnace capable of performing, on a batch system, the pressurized fill process of the wiring film on a plurality (great number) of semiconductor substrates, typically Si wafers, set in the so-called shelved arrangement.
In order to solve the above enumerated problems, this invention provides an apparatus for high-temperature and high-pressure treatment for treating substrates to be treated in an atmosphere of a high-temperature and high-pressure gas which comprises: a pressure vessel; a treating chamber within the pressure vessel; a gas passage for introducing a high pressure gas into the pressure vessel; a heater provided within the treating chamber; a supporting jig for setting the substrates to be treated in a shelved arrangement, the supporting jig allowing a plurality of the substrates to be treated to be inserted into the treating chamber; and a bell-shaped casing surrounding the supporting jig inserted into the treating chamber.
By adopting such a configuration, it is possible to process a plurality of the substrates as a lot and treat the lot of the substrates as a unit under high-temperature and high-pressure conditions.
According to the conventional single wafer type method, substrates were treated one by one. Therefore, contamination such as oxygen and water was generated with each treatment and also dust is produced with each treatment and, thereby, cleanness of the gas used for treatment deteriorated. Since batch treatment can be practiced in the present invention, the above mentioned problems with the related art can be solved. Further, in wiring film processing, the method of the invention can be smoothly combined with existing PVD systems.
Further, in the present invention, the supporting jig is shaped in a cylindrical form, provided with an air hole in its cylindric body portion, and provided with an oxygen getter member or members disposed at top and/or bottom portions thereof.
By adopting such a configuration, oxidization of the substrate to be treated by oxygen as impurity in the treatment gas such as argon and nitrogen can be prevented. Further, heat transfer and gas convection during the treatment can be promoted.
Further, in the present invention, the bell-shaped casing is made up of an inner casing and an outer casing, with a, gas passage formed therebetween, and a gas hole is made in the inner casing at its top portion and an oxygen getter member is disposed in the vicinity of the gas hole or on the gas passage.
By adopting such a configuration, oxygen mixed in the gas passage can be removed and the gas entering the interior of the casing during the pressure treatment can be prevented and, hence, it also becomes possible to recover and reuse the gas used for treatment.
Further, in the present invention, the supporting jig is inserted into the treating chamber by means of a treating stand disposed at the lower portion of the treating chamber and the treating stand is provided with a heat insulating material disposed therein.
By adopting such a configuration, inserting into and removing the substrates from the treating chamber can be made on a batch system so that the treating efficiency can be improved and heat transfer to the bottom lid can be suppressed by the heat insulating material within the treating stand so that the temperature of the bottom lid can be prevented from rising to an extreme level.
As the oxygen getter material, titanium is preferred when the gas for high pressure treatment is nitrogen, and titanium or zirconium is preferred when the gas for high pressure treatment is argon. The oxygen getter member is preferably placed at a position where gas flows well by gas convection. Since the oxygen getter member absorbs the larger amount of oxygen the higher the temperature is, it is preferred to place it in a high temperature position.
Further, in the present invention, by allowing the treating stand with the supporting jig mounted thereon to be inserted into the treating chamber by raising and lowering a bottom lid of the pressure vessel, batch treatment of one lot of substrates as a unit is performed effectively.
Further, in the present invention, the pressure chamber is provided with an opening made therein for allowing a plurality of the substrates moved into and out of the treating chamber by means of the supporting jig, the opening is covered by a cover or a housing made of an airtight material, and an inert gas is allowed to flow into the inside of the cover or the housing.
By adopting such a configuration, contamination by oxygen of the substrates to be treated when one lot thereof as a unit are taken out, can be prevented.
The present invention, by further having an evacuating port and a port valve allowing the port to open and shut, the port and the port valve being disposed at the portion of a top lid or the portion of a bottom lid of the pressure vessel, the adsorbed water by the inner surface and the like of the pressure vessel can be removed in a short time.
Further, the invention may be configured to have a pipe system communicatively connected with the treating chamber for supplying a reducing gas and a stop valve disposed on the reducing gas supplying circuit including the pipe system.
By adopting such a configuration, problems, which have so far been difficult to solve, of oxidization of the metallic film occurring when a substrate with the metallic film formed thereon is taken out into the open air and the accompanying deterioration of fluidity and of the necessity of using a higher pressure than usual to remove the voids when copper is used as the wiring material on account of insufficient fluidity because of the high melting point of copper can now be solved.
Here, it is preferred that an inlet be provided in the bell-shaped casing for allowing the gas supplied from the pipe system to flow into the bell-shaped casing. Thereby, contamination from heating elements can be prevented.
Further, the invention may be configured to have a stocking portion for stocking the substrates to be treated, a transport apparatus for taking the substrate to be treated on the stocking portion into and out of the treating chamber, and an airtight housing for housing the stocking portion, the transport apparatus, and the pressure vessel.
By adopting such a configuration, it becomes possible to collectively house the pieces of high pressure equipment in the housing and achieve good safety control.
Further, the invention may be configured such that a bottom lid allowing the opening portion at the bottom end of the pressure vessel to be opened and shut, a furnace pedestal, and the supporting jig supported on the bottom lid, via the furnace pedestal, are integrally adapted to be taken into and out of the pressure vessel from thereunder and the transport means may be made up of a bottom lid lifting and turning apparatus for raising and lowering and turning the bottom lid, and a shifting and mounting apparatus disposed between the bottom lid lifting and turning apparatus and the stocking portion for shifting and mounting the substrates on the stocking portion onto the bottom lid lifting and turning apparatus.
By adopting such a configuration, it becomes possible to allow plural sheets of the substrates to be treated to enter and exit from the treating chamber while they are set in the supporting jig in a shelved arrangement and to realize effective batch treatment.
Further, the airtight housing may be provided with a gas inlet and a gas outlet for allowing a protecting gas to be flowed through the airtight housing.
By adopting such a configuration, it becomes possible to allow an inert gas or nitrogen gas, as a protecting gas, to flow into and out of the housing.
Further, in the airtight housing, a shielding member for partitioning components of the pressure vessel except the bottom lid of the pressure vessel may be provided.
By adopting such a configuration, even if a dust generating source is present above the substrates to be treated, the dust is prevented by the shielding member from falling on the substrates and sticking thereto.
Further, the airtight housing may be provided with a lid member functioning as a safety valve for relieving the internal pressure of the airtight housing.
By adopting such a configuration, safety can be assured even if the treating gas should leak out of the treating chamber of the pressure vessel.
Further, the invention may have a reducing furnace for reducing an oxidized film formed on the surface of the substrate, the reducing furnace being housed in the airtight housing.
Further, the invention is preferably configured such that a bottom lid allowing the opening at the bottom end of the pressure vessel to be opened and shut, a furnace pedestal, and the supporting jig supported on the bottom lid, via the furnace pedestal, are integrally adapted to be taken into and out of the pressure vessel from thereunder, the transport means is made up of a bottom lid lifting and turning apparatus for raising and lowing and turning the bottom lid and a shifting and mounting apparatus disposed between the bottom lid lifting and turning apparatus and the stocking portion for shifting and mounting the substrates to be treated on the stocking portion onto the bottom lid lifting and turning apparatus, and the bottom lid of the reducing furnace and the bottom lid of the pressure vessel are provided by a common lid and the bottom lid, the furnace pedestal, and the supporting jig disposed on the bottom lid, via the furnace pedestal, are integrally adapted to be taken into and out of the reducing furnace from thereunder.
By adopting such configurations, the problem of oxidization of the substrates to be treated can be solved and the pressure treatment and the reducing process can be effectively performed.